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IBIil96-90, 96-91 <br />developed using "our subsidence prediction irodel" and utilizing the <br />appmodtti3te "35-degree angle of draw you suggested to ire:" <br />As our original calatlations indicate, using the actual <br />extraction ratio, extraction thi.datess, and pertrent hardrock <br />fra`it the geological maps, subsidence would not occur. <br />I11 order to obtain an angle of draw of 34.52 degrees, <br />we had to double the extraction thiGmess (to 15 feet), half <br />the percent hardrnck (to 15$) and assim~e 100$ extraction (ver- <br />sus 31$). The calail.ations are shown on the attached catnuter <br />printout. As you can see even with this theoretical situation, <br />the subsidence would be less than anone-eighth of an inch. <br />We noted that under this scenario that the railroad wand have <br />dropped 9.11 feet as it is located at, the center-of the subsi- <br />dence curve., We.found rso evidence~in the field indicating that <br />the railroad tracks had subsided. [3/] <br />The T3tums hired two professional engineers to assess the ccatditions <br />at their residence. Follaaing a visit on February 23, 1995, William J. <br />Attwooll, P.E., Vice President of ~,;r~ ~+n~*~, Inc., prepared a <br />doaarent for the Thtums, dated March 16, 1995, and entitled "Report of <br />Site Visit Observations Tatum Residence." Therein, he described his obser- <br />vaticros of damage to the interior acri exterior of the residence. He dis- <br />cussed possible causes of the damsge and sumit3rized: <br />[T7 he Tatum residence has been damaged by settlem°nt or dis- <br />placements that are primarily evident in the two-story portion <br />~ In $ 130 IBLA 260, 262-63 n:6 (1994), we stated: <br />"'Atagle of draw' is defined ]n 1 SMR Mininrr~inaar;na Hant9hr,n_k <br />§ 13.1-1 (1973) as 'the angle between a vertical line fran the edge of the <br />[urine] opening and another line extended to a point at which subsidence <br />tails out to zero.' The HaIldbook states fiirrhPr; <br />'This angle has been found to be abort 35° in Europe but is rather <br />academic, being a funeticat of instn~zt precisicat in detecting subsideilwe. <br />Since the subsidence effect is so stall at any point beytmd a 25° angle, <br />this latter may be oonsidered the practical limit of subsidence. Further- <br />imre, indications are that the angle of draw varies with depth arri nature <br />of the strata.' <br />(Footnote omitted). <br />'Angle Of draw' is also defined in $ Di Cti (riL7'V Of i ni na, i noral <br />arr9 uAl?tcri T,?rmc, U.S. Departt[pnt of the Interior, Bureau of Mines 39 <br />(1968), as: <br />'In coal mine subsidence, this angle is asstIIned to bisect the angle <br />between the vertical and the angle of repose of the material aTid is 20° for <br />flat seams. For dipping sei3¢ns, the angle of break in~Ges, being 35.8° <br />from the vertical fora 40° dip. The main break occurs over the seam at <br />an angle frYm the vertical equal to half the dip. "' ,S~ M & ~T ~ ~. v. <br />~, 115 ffi~ S, 21 (1990) . <br />` 157:,~IEQA:293~ ~ <br />